Parametric Design Studies of the Helicopter Rotor Noise using Variable-Fidelity Methods

Abstract

The current trend is to produce even quieter helicopters in order to increase public acceptance. While the ERATO and the from it evolved Blue Edge blade show that noise reduction can be achieved through a specific blade design; the task to arrive at such a design is lengthy. It roughly took 25 years from the wind tunnel campaign to the now flying H160 with this type of rotor design. In order to speed up the design process, it is necessary to quickly and accurately assess the quality of a given design. While a wide range of tools exists to predict rotorcraft noise, the validity as well as the accuracy per computational cost has not been fully evaluated. Recent CFD simulations are able to replicate the BVI noise event, yet are very costly in contrast to wake coupled comprehensive codes. This paper seeks the best method that fulfills the trade-off between speed and accuracy. Therefore, three different rotor wind tunnel models in descent flight are computed with six different ethods. Afterwards, a selection of these methods is utilized in a parametric study to further see how well the different methods can identify the best blade design. The most favored method is a panel method coupled with a free wake model including structural modelling from a comprehensive code, while CFD is recommended only to check the final design due to its high computational cost.